Frying apparatus with compensated thermostat

ABSTRACT

A frying apparatus includes a frypot for containing cooking oil positioned in a support housing. Heating elements are pivotally attached to said housing and suspended within the frypot to heat the cooking oil for deep fat frying. A thermostat is mounted to the front of the housing to extend into the frypot above the heating elements to regulate the cooking oil temperature. The thermostat is separate from the heating elements so that the elements may be pivoted upward to a cleaning position. A biasing heater is mounted to the front of housing directly below the thermostat to compensate for the distance between the thermostat and the heating elements by providing additional heat to the thermostat. A temperature selector is provided on the outside front of the housing to allow adjustment of the thermostat without reaching over the frypot.

Appl. No.: 465,918

United States Patent 1191 [111 3,91 1,250

Price Oct. 7, 1975 [54] FRYING APPARATUS WITH 3,242,849 3/1966 Wells99/41: COMPENSATED THERMOSTAT 3,667,374 6/1972 Ho1mes..... 99/4083,720,155 3/1973 Fritzsche... 99/337 [75] Inventor: George M. Price,Shreveport, La.

[73] Assignee: The Frymaster Corporation, i y EX min rV0l0dymyr Y.Mayewsky Shreve ort, La, Attorney, Agent, or Firml-lubbard, Thurman,Turner & T k 22 Filed: May 1, 1974 er [5 7] ABSTRACT A frying apparatusincludes a frypot for containing cooking oil positioned in a supporthousing. Heating elements are pivotally attached to said housing andsuspended within the frypot to heat the cooking oil for deep fat frying.A thermostat is mounted to the front of the housing to extend into thefrypot above the heating elements to regulate the cooking oiltemperature. The thermostat is separate from the heating elements sothat the elements may be pivoted upward to a cleaning position. Abiasing heater is mounted to the front of housing directly below thethermostat to compensate for the distance between the thermostat and theheating elements by providing additional heat to the thermostat. Atemperature selector is provided on the outside front of the housing toallow adjustment of the thermostat without reaching over the frypot.

7 Claims, 6 Drawing Figures Sheet 1 of 2 3,911,250

US Patent Oct. 7,1975

US. Patent Oct. 7,1975 Sheet 2 of2 3,911,250

FRYING APPARATUS WITH COENSATEI) THERMOSTAT BACKGROUND AND SUMMARY OFTHE INVENTION This invention relates generally to frying apparatus andmore particularly to a thermostat system with biasing heater fortemperature regulation of frying apparatus.

Frying apparatus, such as a deep fat frying system, usually includes afrypot for containing cooking oil with heating coils mounted on the rearwall of the structure and suspended in the oil. A bulb thermostat isnormally attached to the heating coils with a capillary tube extendingupward to the control unit. The heating coils are sometimes pivotallymounted to swing upward and rearward to facilitate cleaning of the coilsand frypot. This arrangement requires that the control unit for thecoils and thermostat be placed on the rear wall so that the coils may beraised without bending the capillary tube. Consequently, an operatormust reach across a hot frypot to adjust the thermostat controls.

Some systems have provided a remote control switch on the front wall ofthe frying apparatus electrically connected to a motor unit whichcontrols a thermostat on the rear wall. Such a system requiresadditional equipment and servicing for the remote control feature.Moreover, accurate adjustment by remote .means is often more difficultand time-consuming than normal manual adjustment.

The present invention provides an operating thermostat mounted on thefront wall of frying apparatus and extending into the frypot above theheating coils for controlling the cooking temperature. This approachallows the use of a differential expansion type thermostat which is muchmore sensitive and accurate than the hydraulic bulb type required if thethermostat is attached to the heating elements. The thermostat isseparate from the heating coils to allow the coils to be pivoted upwardfor cleaning without moving the thermostat. The thermostat and heatercontrols are mounted on the front of the apparatus to allow adjustmentof the controls without reaching across the frypot.

In accordance with one aspect of the invention, a frying apparatus isprovided with heating elements in a cooking basin to heat fluid for deepfat frying. Thermal control means are provided in the basin separatefrom the heating elements for regulating the fluid temperature. Heatingmeans adjacent the thermal control means simulate the temperature of themain heater elements to the thermal control means, compensating for thedistance separating the thermal control means from the main heatingelements by establishing gravity circulation at the same rate as themain elements.

In accordance with another aspect of the invention, a deep fat fryingsystem includes a frypot for containing cooking oil and heating coilspivotally mounted to rotate upward. A thermostat is mounted separatefrom the heating coils and in electrical communication with the coils tomaintain the cooking oil at a predetermined temperature by switching thecoils. A biasing heater adjacent the thermostat provides additional heatto simulate to the temperature of the cooking oil contiguous to thecoils.

BRIEF DESCRIPTION OF THE DRAWINGS For a more complete understanding ofthe present invention and for further objects and advantages thereof,reference may now be had to the following description taken inconjunction with the accompanying drawings in which:

FIG. 1 is a top perspective view of a frying apparatus incorporating apreferred embodiment of the present invention;

FIG. 2 is a top perspective view of a frying apparatus of FIG. 1 withthe heater coils in raised position;

FIG. 3 is a partial elevational view of the frying apparatus of FIG. 1;

FIG. 4 is a side, partially cut-away view of the thermostat and heaterof FIG. 3;

FIG. 5 is an end view of the thermostat and heater of FIG. 4; and

FIG. 6 is a schematic diagram of the control circuitry for the fryingapparatus of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIGS. 1 and 2,a frying apparatus 10 includes a rigid housing structure 12 supporting afront panel 14. A cooking basin 16 is provided in the top of housingstructure 12 behind front panel 14 for containing cooking fluid normallyused in deep fat frying. A back panel 18 extends vertically above therear of cooking basin 16. A suspension plate 20 is connected to extendhorizontally across back panel 18 just above cooking basin 16. Plate 20is positioned to suspend wire mesh cooking baskets (not shown) overcooking fluid in basin 16.

A plurality of heating elements 22 are suspended horizontally near thebottom of cooking basin l6. Elements 22 include two upper coils 24 and26 and a lower coil 28. Each coil is mounted on two cross bar pieces 30and 32 by metal straps 34. A pair of connecting rods 36 are integralwith each coil and extend vertically up the back of cooking basin 16 toattach to a pivot piece 38 at the base of back panel 18. An L-shapedlevel arm 40 extends vertically down the back of cooking basin l6 andthen horizontally to pivotally connect to one of cross bars 32 at pivotpoint 42. A loop 44 is provided at the top of lever arm 40 for pullingthe arm 40 to tilt heating elements 22 upward out of basin 16 as shownin FIG. 2.

An operating thermostat 50 is mounted on an inner sloping wall 15 offront panel 14 and extends horizontally into the lower front portion ofcooking basin 16. Thermostat 50 is mounted entirely separate fromheating elements 22 for independent movement of elements 22. Thermostat50 is preferably a differential expansion-type, as shown in FIGS. 3 and4 for use with a biasing heater as will be described.

A temperature selector dial 52 is mounted on the outer front wall 17 offront panel 14 for selecting the desired temperature for the operatingthermostat 50. A heater light 54 is provided at the center of selectordial 52 to indicate the on-off status of the heating elements 22. A mainon-off switch 56 is positioned on front wall 17 on the right side ofselector dial 52 and is provided with a main indicator light 58 therein.A high limit light 60 is mounted on front wall 17 on the left side ofselector dial 52 to indicate shut down of heater elements 22 because ofexcessive temperatures.

As shown in FIG. 3, two high limit thermostats 66 and are mounted onlower coil 28 by metal straps 68 and 72. Capillary tubes 62 and 64extend down the backside of two of connecting rods 36 from back panel 18to the high limit thermostats 66 and 70. The structure and operation ofthe high limit thermostat system is more fully shown and described in myco-pending patent application Ser. No. 479,761 filed on June 17, 1974.

Thermostat extends into cooking basin 16 in approximately the same planeas the heating elements 22 with the top of the thermostat about A; inchbelow upper coils 24 and 26. With reference to FIGS. 1 and 2, the centercoils 29 of heating elements 22 directly below thermostat 50 are not aslong as the rest of the coils, thereby allowing elements 22 to bepivoted to a vertical position without disturbing thermostat 50. Abiasing heater 51 is provided below thermostat 50 to compensate for thedistance between thermostat 50 and heating elements 22 by establishinggravity flow of cooking fluid to thermostat 50 at or about the same rateas would be established if thermostat 50 were connected to heatingelements 22. Heater 51 is spaced a predetermined distance from thethermostat 50 and has thermal characteristics similar to heatingelements 22 to simulate to thermostat 50 the temperature and gravityflow of the cooking oil contiguous to heating elements 22. A reset shaft126 projects longitudinally from a hexagonal nut member 124 onthermostat 50. A flexible cable 130 connects reset shaft 126 to selectordial 52 on front panel 14.

Referring to FIGS. 4 and 5, thermostat 50 and biasing heater 51 areshown in greater detail. Thermostat 50 is preferably a differentialexpansion-type thermostat comprising a cylindrical tube connected at oneend by a threaded cylinder 122 to nut member 124.

Reset shaft 126 extends longitudinally from the center of nut member 124away from tube 120. Reset shaft 126 is threaded, and has a notch 128extending tranversely across the end 127 furthest from nut member 124.Flexible cable 130 is attached to shaft 126 by connector 131 and extendsto selector dial 52 mounted on front panel 14. Cable 130 is attached toselector dial 52 by conventional flexible coupling means so that cable130 freely rotates in response to dial 52, thereby turning shaft 126.

A lock nut 134 is attached to one hexagonal face of nut member 124 andis provided with a coil spring 136 projecting from the center of nut134. Two insulated conductors 138 and 140 project through the center oflock nut 134 and coil spring 136 for connection to control circuitry 78shown in FIG. 6. The other ends of conductors 138 and 140 extend insidecylindrical tube 120, each conductor connecting to one of a pair ofdiametrically opposed contact points 142 and 144. Points 142 and 144 areeach suspended on metallic strips 146 and 148 extending substantiallythe length of the cylindrical tube 120. Strips 146 and 148 are held bymounts 150 and 152 located at either end of tube 120. Contact points 142and 144 are insulated from metallic strips 146 and 148 by plasticinsulating sheaths 154 and 156 overlying strips 146 and 148.

Biasing heater 51 is mounted below thermostat 50 in the inner front wall15 of front panel 14. A threaded shaft 160 is screwed into a bore 162 inthe inner front wall 15. A nut 164 is concentrically mounted on threadedshaft 160 and tightened into a recess 166 in the front wall 15 in orderto hold biasing heater 51 se- @urely in place. Heater 51 comprises acylindrical tube 170 extendin horizontally into the interior of cookingbasin 16 below thermostat 50. A heating element 172 extendssubstantially the entire length of biasing heater 51 and is connected tocontrol circuitry 78 by insulated conductors 174 and 176. Heatingelement 172 has thermal characteristics, such as watt density andthermal mass per unit length, similar to the main heating elements 22 inorder to simulate the dynamic response of elements 22. The distance D1between biasing heater 51 and thermostat 50, and the material andstructure used in the heater are precisely determined in order toaccurately follow the temperature of heating elements 22 with a minimumof overshoot or stepping up as is often seen with heavy biasing, and toinsure rapid response to temperature changes.

FIG. 6 discloses the electrical circuitry 78 employed for automaticallyregulating and limiting the cooking and cleaning processes usingapparatus 10. Electrical inputs 80, 81 and 82 are connectedthrough acontactor having contacts 84a, 84b, 84c, 84d, and a reverse contact 84e,and a contactor having contacts 86a, 86b and 860, to heating elements 22comprising upper coils 24 and 26 and lower coil 28. A contactor coil 88is positioned to activate contacts 84a, 84b, 84c, 84d, and 842, and acontactor coil 90 activates contacts 86a, 86b and 860. A circuit breaker92 is connected between input line 82 and circuitry 78 to prevent damagefrom overloading. The other side of circuit breaker 92 is connected inparallel to contact 84d and a reset switch 96. An on-off switch 56 isprovided at the output of contact 84d and switch 96. Main indicatorlight 58 is connected between the on-off switch 56 and neutral. Highlimit thermostat 66 is also connected between reset switch 96 andneutral through contactor coil 88.

The other side of on-off switch 56 is connected to a two-way functionswitch 98 having an upward position with post 100 for a cooking functionand a downward position in contact with post 102 for a cleaningfunction. Connected to post 100 in series are high limit thermostat 70and operating thermostat 50. On the other side of thermostat 50,connected in parallel, are biasing heater 51, heater light 54, andcontactor coil 90. Connected to post 102 of function switch 98 is atwo-way delay relay switch 106 having an upward burnoff position when incontact with a post 108 and a downward delay position when in contactwith post 110. Connected to post 110 is a heater resistor 112 whichoperates in association with delay relay switch 106. Heater resistor 112is in turn connected to neutral. Reverse contact 84e of contactor 84 isconnected between circuit breaker 92 and neutral through high-limitlight 60 and closes when thermostat 66 or 70 open contact 84 because ofa high temperature condition.

In operation, power is impressed on control circuit 78 through inputs80, 81 and 82. Circuit breaker 92 is normally closed. When reset switch96 is depressed, contactor coil 88 is activated to close contacts 84a,84b, 84c and 84d and to open reverse contact 84c. A circuit ismaintained through hihg limit thermostat 66 by contact 84d which willcontinue to hold until interrupted by a power loss or a high temperaturecondition opening thermostat 66. The frying apparatus 10 is placed inoperation by closing on-off switch 56. Selector dial 52 is turned tochoose the desired cooking temperature to be maintained by thermostat50. With heating elements 22 positioned in the cooking basin l6, switch98 is in the upward cooking position in contact with post 100. Byactivating switch 56, contactor coil 90 is energized, which closescontacts 86a, 86b, and 86c and supplies power to heating elements 22.Biasing heater 51 and thermostats 70 and 50 are also actuated. Asheating elements 22 warm the cooking oil, biasing heater 5], togetherwith elements 22, provides heat to operating thermostat 50 to simulatethe temperature of the cooking oil in the immediate vicinity of elements22. As thermostat 50 becomes warmer, the cylindrical tube 120 expands,causing the distance between mounts 150 and 152 to increase slightly.When the preselected cooking temperature has been reached, thecylindrical tube 120 has expanded sufficiently to separate contactpoints 142 and 144, thereby opening ther mostat 50. Contactor coil 90 isde-activated, opening contacts 86a, 86b, and 86c and cutting off powerto heater elements 22 and to biasing heater 51. As the cooking oil coolsbelow the preselected temperature, thermostat 50 cools accordingly andpoints 142 and 144 come back into contact. Heater elements 22 andbiasing heater 51 are thereby energized and the process is repeated.

The operation of the circuitry with respect to high limit thermostats 66and 70 does not comprise a part of the invention for the purpose of thispatent application, and it is discussed in my co-pending patentapplication Ser. No. 479,761 filed on June 17, 1974.

It should be understood that other types of thermostats may be usedwithout departing from the spirit of the invention. For example, abulb-type thermostat utilizing capillary tubing may be mounted on thefront of the frying apparatus in place of the thermostat shown. Thedifferential expansion type thermostat is preferable because it offersextremely sensitive control and rapid response to changes. Moreover,this type of thermostat is relatively inexpensive and sturdy compared tosome other more fragile types. Likewise, other types of thermal biasingmeans may be used besides the cartridge-type biasing heater shown,without departing from the spirit of the invention.

It is understood from the foregoing description that the compensatedthermostat system of the present invention provides several importantadvantages over other systems. The thermostat is mounted separately fromthe heating coils to allow the coils to be pivoted upward without movingor risking damage to the operating thermostat. Moreover, the thermostatand heater controls are mounted on the front panel of the fryingapparatus so that an operator may adjust the controls without reachingover a hot frypot during cooking and without coming near the hot coilsduring pyrolytic cleaning. A biasing heater is provided below theoperating thermostat to compensate for the separation between thethermostat and heating coils and insures accurate operation of thethermostat.

Although a particular embodiment of the invention has been illustratedin the accompanying drawings and described in the foregoing detaileddescription, it will be understood that the invention is not limited tothe embodiment disclosed, but is capable of rearrangement, modificationand substitution without departing from the spirit of the invention.

What is claimed is: 1. In frying apparatus having electrically operatedheating elements disposed in a cooking basin to heat fluid in said basinfor deep fat frying, the combination comprising:

adjustable thermal control means in electrical communication with saidheating elements and disposed in said basin spaced separate from saidheating elements for regulating the temperature of said fluid bycontrolling said heating elements, and

heating means in electrical communication with said heating elements andadjacent said thermal control means for heating said thermal controlmeans to the temperature simulate said heating elements being adjacentsaid thermal control means, whereby said fluid is maintainedsubstantially at a predetermined temperature by said thermal controlmeans.

2. The apparatus of claim 1 wherein said thermal control means comprisesa thermostat mounted on the front of said apparatus spaced apart fromsaid heating elements.

3. The apparatus of claim 2 wherein said thermostat comprises adifferential expansion thermostat having a shaft for manual selection ofsaid predetermined temperature.

4. The apparatus of claim 1 wherein said heating means comprises abiasing heater disposed below said thermal control means and havingthermal characteristics similar to said heating elements.

5. The apparatus of claim 4 wherein said biasing heater has a wattdensity and a thermal mass per unit length substantially the same assaid heating elements.

6. The apparatus of claim 4 wherein said biasing heater is electricallyconnected to said heating elements whereby said heater is actuatedwhenever said heating elements are turned on.

7. In frying apparatus having electrically operated heating elementsdisposed in a cooking basin to heat fluid in said basin for deep fatfrying, the combination comprising:

thermal control means in electrical communication with said heatingelements and disposed in said basin separate from said heating elementsfor regulating the temperature of said fluid by controlling said heatingelements, and

heating means in electrical communication with said heating elements andadjacent said thermal control means for heating said thermal controlmeans to simulate said heating elements being adjacent said thermalcontrol means, whereby said fluid is maintained substantially at apredetermined temperature by said thermal control means,

said heater elements being attached to said apparatus so as to pivotupward toward the rear of said apparatus, and said thermal control meanscomprising a thermostat mounted on the front of said apparatus abovesaid heating elements whereby said elements may be pivoted to saidupward position with- UNITED STATES PATENT OFFICE CERTIFICATE OFCORRECTION PATENT NO. 3, 911,250

DATED October 7, 1975 INVENTOR(S) George M. Price It is certified thaterror appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

Col. 4, line 58, "hihg" should be --high Col. 6, line 14 "thetemperature simulate said heating elements should be -simulate the.temperature of said heating elements-- Signed and Sealed thistwenty-seventh D a) January 1976 [SEAL] Attest:

RUTH C. MASON C. MARSHALL DANN Arresting Officer Commissioner oj'larenrsand Trademarks UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTIONPATENT NO. 2 3,911,250

DATED October 7 1975 INVENTOR(S) George M. Price It is certified thaterror appears in the ab0ve-identified patent and that said LettersPatent are hereby corrected as shown below:

Col. 4, line 58, "hihg" should be -high- Col. 6, line 14, "thetemperature simulate said heating elements" should be simulate thetemperature of said heating elements-- Signed and Scaled this twentye Da) Of January I 9 76 [SEAL] Attest:

RUTH C. MASON C. MARSHALL DANN Arresting Officer Commissioner ofParentsand Trademarks

1. In frying apparatus having electrically operated heating elementsdisposed in a cooking basin to heat fluid in said basin for deep fatfrying, the combination comprising: adjustable thermal control means inelectrical communication with said heating elements and disposed in saidbasin spaced separate from said heating elements for regulating thetemperature of said fluid by controlling said heating elements, andheating means in electrical communication with said heating elements andadjacent said thermal control means for heating said thermal controlmeans to the temperature simulate said heating elements being adjacentsaid thermal control means, whereby said fluid is maintainedsubstantially at a predetermined temperature by said thermal controlmeans.
 2. The apparatus of claim 1 wherein said thermal control meanscomprises a thermostat mounted on the front of said apparatus spacedapart from said heating elements.
 3. The apparatus of claim 2 whereinsaid thermostat comprises a differential expansion thermostat having ashaft for manual selection of said predetermined temperature.
 4. Theapparatus of claim 1 wherein said heating means comprises a biasingheater disposed below said thermal control means and having thermalcharacteristics similar to said heating elements.
 5. The apparatus ofclaim 4 wherein said biasing heater has a watt density and a thermalmass per unit length substantially the same as said heating elements. 6.The apparatus of claim 4 wherein said biasing heater is electricallyconnected to said heating elements whereby said heater is actuatedwhenever said heating elements are turned on.
 7. In frying apparatushaving electrically operated heating elements disposed in a cookingbasin to heat fluid in said basin for deep fat frying, the combinationcomprising: thermal control means in electrical communication with saidheating elements and disposed in said basin separate from said heatingelements for regulating the temperature of said fluid by controllingsaid heating elements, and heating means in electrical communicationwith said heating elements and adjacent said thermal control means forheating said thermal control means to simulate said heating elementsbeing adjacent said thermal control means, whereby said fluid ismaintained substantially at a predetermined temperature by said thermalcontrol means, said heater elements being attached to said apparatus soas to pivot upward toward the rear of said apparatus, and said thermalcontrol means comprising a thermostat mounted on the front of saidapparatus above said heating elements whereby said elements may bepivoted to said upward position without moving said thermostat.